math/e_scalb.c

   1 /* Copyright (C) 2011-2014 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <fenv.h>
  20 #include <math.h>
  21 #include <math_private.h>
  22
  23
  24 static double
  25 __attribute__ ((noinline))
  26 invalid_fn (double x, double fn)
  27 {
  28   if (__rint (fn) != fn)
  29     {
  30       feraiseexcept (FE_INVALID);
  31       return __nan ("");
  32     }
  33   else if (fn > 65000.0)
  34     return __scalbn (x, 65000);
  35   else
  36     return __scalbn (x,-65000);
  37 }
  38
  39
  40 double
  41 __ieee754_scalb (double x, double fn)
  42 {
  43   if (__glibc_unlikely (__isnan (x)))
  44     return x * fn;
  45   if (__glibc_unlikely (!__finite (fn)))
  46     {
  47       if (__isnan (fn) || fn > 0.0)
  48         return x * fn;
  49       if (x == 0.0)
  50         return x;
  51       return x / -fn;
  52     }
  53   if (__glibc_unlikely (fabs (fn) >= 0x1p31 || (double) (int) fn != fn))
  54     return invalid_fn (x, fn);
  55
  56   return __scalbn (x, (int) fn);
  57 }
  58 strong_alias (__ieee754_scalb, __scalb_finite)